Methods for heat-treating molybdenum-base alloys



Patented May 25, 1954 METHODS FOR HEAT-TREATING MOLYBDENUM-BASE ALLOYS John L. Ham, Dearborn, Frederick P. Bens and Alvin J. Herzig, Detroit, and George A. Timmons, Ferndale, Mich., assignors to Climax Molybdenum Company, New York, N. Y., a corporation of Delaware No Drawing, Application October 6, 1951, Serial No. 250,201

6 Claims. 1 I

This invention relates to refractory metal a1- loys and more particularly to cast, heat-treatable alloys containing molybdenum and beryllium and to a method of heat treating the same; and the present application is a continuation-in-part of applicants copending application, Serial No.

218,527, filed March 30, 1951, now abandoned.

The alloys of the present invention are especial- 1y useful in applications of the type which require a material to retain its high hardness, strength a or resistance to creep at elevated temperatures.

Applications of this type include points for piercing seamless steel tubing, electrodes for heatingmolten glass, die-casting dies for brass and other metals, etc.

An American Society for Metals publication, preprint No. 33 of 1949, by Kessler, and Hansen, reports on experiments with molybdenum-chromium alloys, a few of which contained between .1% and .2% beryllium and no carbon. The report does not mention any forging tests on beryllium-containing alloys and it indicates that while some increase in hardness resulted from beryllium additions, no precipitation or age hardness was obtained.

The principal objects of this invention are to providecast molybdenum-base alloys which are capable of being worked at elevated temperatures; to provide cast molybdenum-base beryllium-containing alloys which are capable of being worked or machined into the desired shape and form and thereafter hardened materially by heat-treatment; to provide a method for heattreating such alloys that will markedly increase their hardness; and, in general, to provide improved molybdenum-base alloys which are characterized by high temperature properties superior to those of heretofore known materials.

The terms cast and "casting as used in this specification are intended to designate the product resulting from the melting of metal and solidifying the same in a mold whether or not themetal has been subjected to subsequent working or machining. The term casting is also used to designate any process or method which involves melting metal and solidifying the same in a mold.

It has now been found that certain molybdenum-base alloys containing beryllium are age or precipitation hardened when subjected to the hereinafter described heat-treatment, and that improved high temperature properties are induced by such heat-treatment and are retained at elevated temperatures even after prolonged periods of time. Such heat-treatable alloys may 2 be cast, annealed, then fabricated into the desired shape and thereafter hardened by the heattreatment. This invention is also concerned with molybdenum-base alloys containing beryllium which are subject to heat-treatment in accordance with this invention but which are not capable of being worked by forging, rolling, pressing, swaging, drawing, etc. Such unworked alloys are useful in the as-cast form after heattreatment, and in some applications may be used without heat-treatment.

If the alloy is to be worked at elevated temperatures, it may contain up to a maximum of 25% beryllium. It has not been possible to hotwork alloys containing more than .25 beryllium. However, larger quantities of beryllium may be present if no working is required.

Cast molybdenum-base alloys containing small quantities of oxygen cannot be worked at elevated temperatures if molybdenum oxide is segregated at the grain boundaries of the cast alloy since that oxide materially reduces intergranular cohesion. Small quantities of carbon or aluminum appear to overcome this defect when the amount of oxygen is limited. Similarly, it is found that in the presence of beryllium within the limits contemplated by the present invention, alloys capable of being worked at elevated temperatures are obtained even though no carbon or aluminum is present. While the reasons for this phenomenon are not fully understood, it is believed that oxides of beryllium replace those of molybdenum, and that the beryllium oxides are less detrimental. In any event, alloys containing from .001 to .25% beryllium and not more than .05% oxygen can be worked at elevated temperatures to a beneficial degree if the beryllium is present in an amount at least sumcient to react with all the oxygen to form beryllium oxide.

' Although not essential, it is preferred that the molybdenum-beryllium alloys of the present invention also contain small quantities of carbon and/or aluminum. These elements, aside from the beneficial effect upon the forging characteristics, have the effect of increasing the strength of a sintered rod formed of the powder materials employed in the'alloy and thus facilitate the practice of forming a casting by using such a sintered rod as a consumable electrode in an arc furnace. Moreover, carbon in amounts of about .02% or more makes it possible to employ lower temperatures in the heat-treatment hereinafter described. Thus, cast alloys of the present invention which are capable of being worked at carbon and aluminum are present it is desirable.

to further restrict the maximum carbon content as the aluminum increases towardfif.4-%'; tliepreferred alloy contains not more than' '.02%' carbon.

In all cases, workability improMesrwith.-reduc-...

tions in the oxygen content andu-thelmaximumm permissible quantity in anaalloy that' is--.:.-to"be*: worked at elevated temperatures is about .05%.

It has not been found practical, irLthe production of large cast ingots of molybdenum-basealloys to reduce the oxygen content below about .001'%I' Molybdenum-base alloys containing aluminum .1,

and no beryllium are disclosed and claimed in applicantsiz copending ,application,.-.l .Seriab. No. 250,202,. filed October 6; .1951, .orr -Molybdenum-t-n Tungsten-Aluminum Alloysi:

Molybdenum .-b eryl-lium .alloysr arevsusceptibler toaage 101' precipitation-a hardening... Beryllium? has .limitedsolubil-ity-inemolybdenum in thevsolid state the-solubility of -.-beryl-lium increasesa-withe increasing,temperature; a .Togainathe .iullhardw eningr from: the g-heatrtreatment; it -is:.-necessar-y that a certain .eminimum quantity: oi berylliumrz. be present. To preserveeworkability;-it tie-deer sirable to employ thetlo-West beryllium content which. :wil-lprovide the .desired hardeningefiiect. from theiheat-treatment Since; a: part of: the beryllium: .--in--. any giver-11 molybdenumabasealloy; mayebe combined-.-.-withr; some of the oxygenwpresentetoeforml-beryllium; oxide, and in that acasewo-uld -.,-bez-ineff.ective asa. hardening agent, the-total. amount of beryllium touproduce a given-.hardening effect-.varies with. the amountofi oxygen .the: final-alloy. Inhale-2 1057,35 containing -minimum oxygen; i. eat in .-the i order of .001--% o-xygen,-astlittle.as*z03-% beryll-iurm. will produce asignificant. increaserin wthelas-castf hardnessas: well 2,8218, significant-amount .'O fage. or p-recipitation.-:hardness When the moxygem content is "atr-its maximum-zpermissibleevalue .of-& .05 %-,approximately 1108 73 berylliumlwi-llz'be re-vquired =-tor-produce anrequivalenteffectw Quanse tities .-below-:.03% l arexinsumcient to provide-sig l: nificantnhardening on heat-treating and.iquan+= tities above; render thenmaterial sincapable of; being", workedto :a beneficial degree; Where: theralloy-is:tozbe-usedwin the unworked; conditiom:

theberylliumccontentim'ay' be,increased toia-rmaxs Agehardnessds .induced incthese:al1oysby;.hold-, ingthem'tatan.eleyated; temperature ion-a period 7 sufficient 'tocincrease: the-amount Uf .b eryllium: solution, quenching the alloy, reheating it ,toza. suitableitemperature,2 andmo lding it at-thelatter temperature fora--.periodrofctimev- The: temperaw' turevfrom; whicl'rathe: alloy v is: quenched rissheree inafterrreferredito 'as the "Jsolutionirtemperaturep and: thetemperature to which :the'; alloy is raised", after quenchingzis referredrztotasztheiiaging item-2'; perature.

Both time and temperature "affect thezamount" of beryllium-whichtgoesinto solution"; Thesolue tion rate increases Lrapidlywvith increases intern-iperature: and; therefore, --:in order tor-avoid, :pI'Q'r? longed heatinguitis preferredto zuseethe highest: practical solution;temperatures-s 1 In additiongthe a total .zamounteof beryllium .has arr-,effectnmthe. solutionsrate,:- larger ..quantities .incneasingg: the.

rate. Therefore, lower temperatures and shorter solution periods may be employed with larger quantities of beryllium. In addition, it is found thatlthelcarbon oontentlias annimportant effect on the'solution temperature, lo-vrt carbon alloys requiring higher solution temperatures than higher carbon alloys, all other things being equal. The maximum amount of beryllium which will gojntosoiidi'sol'iition with molybdenum containperature isvabout .05% and, consequently, larger quantities ofb'erylliiim are employed primarily to reducevthe solutionetemperature or the holding time-tor bother;

Insapplyingrzzthecrabove principles to practical needs, it is foundthat where it is possible to produce'iovvoxygenalloys, as little as .03% berylliu'm will effect a small but significant amount of agee'on;precipitation hardness. However, it is necessary to use very high solution temperatures onholdithe alloy atritsesolution temperatureefor alpnolongedsperio The preferred; solution-temn: perature; fonsuch .--a galley weu-ld cbeeabout. 3800 F gwithiaholdingmeriodirr the order of'sfourato" six hours; With. this-treatment; thera gethardnessl will: be .-in creased:- if. vat-:least 02% carboneis-.pres:-.-- ent. 1 As-the-.-oxygen content increases from its practical minimum of =1 001%, the amount? of beryllium nshouldmbe increased; .the added-beryl-w lium'being at leastthat (required to combinea-witli theincreased. oxygentoform.beryll-iumoxides- Agehardness :is obtained only ifethesmin-imum. beryllium.:contentincreasescfrome-.03 %,.rto 08% the oxygen ,content 2111612881585: from-i400 1% to: its: maximum of 05%. In view of thedesirabilitytofl reducing: the solution/temperature 1 and timav it isspreferredeto emplomberyllium in fazeminimu-me amount which increases --from-..05% .-tow.1 as=,the oxygen: content-increases from .001 :to itsmaxie' 'mumwf '.05% arhigh degree;-otlprecipitatiom more carbon-.- ispreferably; heldat= asolution teme r perature of abet-$8350? F.-\for--threeato fouruhoursand: then: quenched; An: .alloy. containing -.l5% beryllium andiabout 502%", 01' moreecarbon is .preferably held at; aesolution .-temperature of about 3350"1F; for-:abouttwo tozthreeehours. I alloy; containing :15 %--.beryllium--andlas little as- .0.06-%- carbon .is pref erabiyhe'ld at; a solution tempera?-- ture of about-3800 FzrfOl aboutetwohourszor 3600 -F. for about.six"hours.-7 If -maximum hard.- f ness is not required, the holding. period.-and :solnew tion temperature-may \be meduced-i- In" all cases a-solutio-n--.temperature.- of at :least 3200 F: is .req-uiredeto Lproduceesignificant age 01?I precipitatioim hardnesss; Highest solution' tem.-. peratures 'tharrt-hoserspecifiedaboveinay;beeem. ployed, .but careeshouldi beltaken'to avoidz hold-z ing the 'alloy* at: 'a temperaturawhich rwillwmelt any substantial portion; The timezfor-x-which the alloys of the present: inventionmay-baheldat the F solution temperature is limited only by thelprac- -J tical consideration i.1that-.-equilibrium approached asymptotically =with.time: The solution heat-treatment shou1d=;be..carried.out underlsubm stantially vnonoxidizinge. conditions... i.- .e., inan.

longed period of time.

retain a supersaturated solution of beryllium.

This rate may be attained in pieces of about onehalf inch controlling section by cooling in still air, and in larger sections by quenching in oil or water.

,The alloy is next subjected to a temperature in the range of about 1600 F. to 2000 F. for a pro- The time required depends primarily upon the temperature employed. For example, maximum hardness has been obtained by employing temperatures of 2000 F. for a time of only forty minutes with an alloy containing .15 beryllium, 033% carbon and the balance molybdenum. About six hours at 1750 F. is required to obtain maximum hardness with the identical composition. At 1500 F., substantially less than maximum age hardness was developed in sixty-six hours, although the hardness was still increasing at the end of that period. In general, the lower the aging temperature used, the greater the ease of control and the longer the time required to attain maximum hardness; but it willbe apparent that the temperature and time selected will depend upon considerations of practical convenience and the particular requirements of the application. To produce any significant age hardening it is necessary to hold the alloy at least fifteen minutes at 2000 F. or three hours at1600 F., the time increasing as the holding temperature decreases from 2000 F. to 1600 F. The preferred aging temperature is in the neighborhood of 1800" F., at which temperature maximum age hardness may be produced in from two toeight hours. During aging the alloy should be protected against oxidation by means such as an inert atmosphere, a hydrogen atmosphere, a vacuum, or immersion in a molten salt bath.

The hardness developed in molybdenum-base alloys containing beryllium bythe above-described heat-treatment is decidedly higher than that obtained in any hitherto known, forgeable molybdenum-base alloys. Thus, in general, the hardness which may be achieved exceed 500 V. P. N. (Vickers Pyramid Numeral) if beryllium is present in amounts of or more.

If desired, instead of quenching to room temperature and then reheating, the alloy may be cooled fairly rapidly from the solution temperature to the aging temperature and then aged. For this purpose, the alloy may be quenched in a molten metal or molten salt bath to a temperature at or below the aging temperature. 1

As set forth in the application of Norman L.

Deuble, Serial No. 234,465, filed June 29, 1951,

an oxidation resistant coating may be formed on molybdenum-base alloys by dipping them in a molten bath of aluminum containing from 5% to 50% silicon. Thus, a bath, at a temperature between 1350 F. and 2000 F, may be employed as a quenching bath in the heat-treatment of the present invention and the resulting quenched alloy may then be aged in an oxidizing atmosphere. The preferred practice is to use an aluminum quenching bath containing from to silicon at a temperature of 1350 F. to 1600 F. and then age the alloy at about 1800 F. The use of a quenching bath of molten metal which will. form an oxidation resistant coating may be applied with advantage to any molybdenum-base alloy that is capable of developing age hardness.

Tungsten and molybdenum form a continuous series of solid solutions. The addition of tungsten to molybdenum causes a mild increase in the elevated temperature hardness and reduces the capacity of the alloy to be worked at eletemperatures.

vated Molybdenum-berylliumtungsten alloys which are capable of being worked at elevated temperatures and of developing age hardness may be obtained if, as the tungsten percentage approaches a maximum of about 50%, the amount of berylium is proportionately reduced from its maximum of 25% toward its minimum of .03%. It is preferred to use no tungsten or to maintain the tungsten content below about 10%.

Age hardness is obtained by the above treatment when beryllium is present in molybdenumbase alloys as long as, in a given alloy, molybdenum is present in an amount exceeding the amount of tungsten present, if any, and the total of the molybdenum and tungsten constitutes at least 70% of the alloy. Other elements may also be present. Thus, certain hereinafter-listed transition elements produce advantageous effects when added to the molybdenum-berryllium alloys which are capable of being age hardened by the process of the present invention. However, to produce an alloy which can also be worked at elevated temperatures to a beneficial degree, the amounts of tungsten, other transition elements, aluminum and berryllium must be limited; the preferred alloys contain at least molybdenum. Thus, even in pure binary alloys of molybdenum, the following advanta geous transition elements should not be present in amounts exceeding the following percentages of the alloy is to be worked at elevated temperatures:

num in amounts in excess of .4% and up to a maximum of 2.5% have an efiect on workability similar to that of the above transition elements. They all produce a proportionate increase in solution hardness at 1600 F. as their quantities increase toward their maximums. The maximum amounts given for aluminum and each of the transition elements other than tungsten correspond roughly to those quantities of each element which, when added alone to molybdenum, will produce a hardness at 1600 F. of 200 V. P. N. in an annealed casting. Beryllium alone in the amount of 25% has the same eifect. It has not been possible with normal working tech niques to achieve a worthwhile percentage of recovery from the working of molybdenum-base alloys having hot hardnesses above that value, but a beneficial working at temperatures substantially above 1600 F. may be performed on the alloys of the present invention, provided the hardness at 1600 F. does not exceed about 200 V. P. N. in an annealed casting. The eifects of all the above-mentioned metals, including tungsten, are additive and, therefore, when any two are present, the maximum permissible amount of one should be proportionately reduced from the stated maximum given above to the extent that the other metal approaches its stated maximum if the alloy is to have the capacity of being worked atjelevated temperature to a beneficial degree. Stiiidfurther reductionsmonisthecsame'i Etifampldifi'mbasis musttoe madeiifmore ithanrtwos are present-,4 tents and 111 all 'cases less than theseemaximums'gives:- Brymumm thesbestsresults; s- Tungsten For the-purpose of obtainingmaximum:hard! 0 Carbon. 4 'ne'ss-iahd *strengthi atweleva'tedtemperatures -in i gf' I balance, molybdenuml base. alloys'iwhichacontam beryllium. i T T and-uwhioh are wellradapte'd' to hot-workingsthe- Emample 7 preferred alloying transition Felements-\;aretita-: Per-scent; nium;= co1umbiun'i; vanadiumgfzirconiumandttahl0 ;Berylliumxunhfin g talumw Molybdenum base 1' alloys "characterized Carbon; primarily byflthe-beneficial efiects of these'ele ments', respeict-ively, are more fully disclosed and. Molybdenum balances claim'ed iiri -applicants'copen'ding'- applications" filedai'concurrentlyi :herewith, as followsz: Serials: E Example ,8 N011 ,:G;2M';" "MolybdenumaTitaniumz Alloysf'; cent; SriaLNor250$267; Molybdenum Columbium-'Al-+ y l d a 137;, 1098; Serials- N6: 250,203,:Molyhdenum var a-. ca g cliumiiil'loys Serial-:Nov 250,206; Molybdenum- Aluminum; 5 Zirconium Alloysi; Serial No.- 250,-205; '.Molyb+-E y n balance;

denum-Tantalum; Alloysfi;

Therefore; therexpressionwmolybdenum-base I alloyi-asmsed in thefoliowing' claimsjmeansxunzless otherwise:specified-that the-alloy is atleast 70%211I101Ybfl811l11ri or=molybdenum andtungsten with Ethe molybdenum": exceeding the tungsten,- but other "elements may i beipresent in'xamounts 1 which" do notmaterially vimpair' theage-harden ingm'characteristics of molybdenum-beryllium al- IOYS.

Alumirri'irrr:fin v amounts xabove r .4 72, and: the. above transition elements, other than tungsten, when present will usually reduce the temperature at'which' a liquid phase appears and, consequent- Iii-may "necessitate "thejuse of "somewhat lower 3 solution temperatures which approach 3200 as a minimum." The maximumsafetemperatures can be determined readily by trial.

The following 'specific""examples are given by; wa of "illustrati'onwo "show" molybdenumeberyp li'um alloys which'have' compositions within" the: above specified' ra'nges and to" which" the heat-H treatmentof" this invention is applicable:

The effect of "heat-=treatment ion the alloysiof 1f this inventionimay .be"i1lustrated"bytthe 'first'fexr ample'given above, That alloy,"having a hard-'1'.

,nessof::230 V. P."N."in'the annealedcastingwas raised. .toa temperature "of 3600 F. and oil quenched after "beingcmaintained 1 at that ';tem'- perature." for two" hours. Thex'hardness".after quenching was 1430 P.1N1" After heating at 1 17509 F. for seven hours; theroom"temperature hardness of the al10y:was increased'to'68O VIP. N'. A second'sam'ple'"ofpthe same composition; subjected to the first two'steps of the "heatetreatment; was 'then heated at' ZOOO 'F. for forty"; minutesand attainecliahardnessof "'67 5 'V. PTN.

A" third sample "*of' identical composition; 'after" quenching from 3600F., was heated at 1500" for'sixty six hours anda hardness-of 520 V. PIN. was reached.-.. v

This *he'at-treatmenralso improves the hot hardness of "the alloy; The hot-hardness, as"- well as room temperature *hardness', is "retained by-the -alloyi for "substantial periods of time on" exposure to elevated temperatures." The "alloy' Example '1' of Example 1, after being fully hardened; hada Per went; hardness of 680 V. P. -N. v at room" temperature Berrymumv and a hardness'of 520W." P. --N. at'160'0 Its Carbonu h D331. hardness" Was :fully retained' after longexposure Molybdenum; balance" at 1500 F. and showed very'little' reduction after" Earample z 1 Although the hardness induced by heat-treat- Per cent: ing is retained for 'a-long' period at- 1600"'-'l1";,"the

Berymumr: V I I j nducedagehardness'may' be'removedbyheat- Carbon "I f ing' 'to a temperature hetween-2200 F. and 3000"" f. N ig and'furnace cooling. This-characteristic of M61575 i "ff a1 ance'; molybdenum-base alloys containing beryllium above .03% is particularly beneficial 'inthe re-y' gwamplevg v. spect -thatthe hardness-of the'alloy may be re ducedto facilitatefabrication operations and Berymumvy there a afi'ier increasedto meet service requirements. aarbbnrw 7 Cast molybdenum berylliu'm alloysmay he"- produced i'n"accordancewit-hthe followingproca I Molybdenum balance ess:*(1') mixing molybdenum;'berylliiim'andanyx other desired'- elements in "theform "of powders;

I v in the' desired-proportions; (2) pressing the mix- Per cent tureinto successive-pellets to form a continuous rod; (3) 'sintering the'rod to impart sufficient" PWEmPm 1- p strength to th'e'sameto render it self-supporting;

Molybdenum balance and"(4=) arc-meltingthesintered'rodasa con- Example 5 ,,.,sumable electrode in'an inert "atmosphere and h collecting the metal directly'in a water-cooled Per ce copper mold."

Berylliurri' .05 Inthis process, the'starting materials-used are Aluminum- .10 commercially pure molybdenum --powcler. pref Carbon .01 erably'containingnot more'than'about ;05%-*oxy-' 1 1 71 mm balance 'geneand' commerciaily'availableberyllium pow 9 der. Metals in the form of small chips or granules may comprise part of the charge.

The" powder charge is fed into an extrusion die positioned beneath the ram of a reciprocating press wherein successive pellets or layers of the powder material are pressed continuously on top of preceding pellets to form a continuous rod of pressed metal powder. Adequate compaction of the pellets is obtained by using pressures of 10,000 p. s. i. to 20,000 p. s. i., with 14,000 p. s. i. normally being adequate. Pressing, sintering and arc-melting are preferably performed within the same container in an inert atmosphere such as argon or helium.

Suificient strength to make the pressed metal rod self-supporting is imparted by sintering the rod at a temperature of 2400 F. to 2900" F. for approximately a quarter of a minute to several minutes. In some cases, difliculty has been encountered in making a molybdenum-beryllium rod which was self-supporting in the absence of carbon and/or aluminum. The explanation for this phenomenon is unknown but, when the difficulty is encountered, it may be remedied by incorporating in the powder metal mixture .01% or more carbon or .01% or more aluminum. Sintering may be accomplished by any desired method of heating. Electrical resistance heating has been employed successfully.

The sintered rod is then used as a consumable electrode in an inert atmosphere arc furnace. Melting is started by striking an arc between the rod and a starting electrode comprising a pile of chips of the same or similar alloy placed on a disc of molybdenum at the bottom of the casting mold. A water-cooled copper mold has been successfully used for receiving the molten molybdenum alloy without contaminating the alloy with copper. Molten alloy striking the watercooled copper mold quickly solidifies, forming a protective coating on the surface of the mold. Thereafter, the liquid alloy becomes the lower electrode and the upper, consumable electrode is mechanically fed toward the lower, liquid electrode to maintain continuous melting with the proper arc spacing.

If the alloy is to be worked at elevated temperatures, it is necessary to avoid the introduction of significant quantities of oxygen as a contaminant in the inert atmosphere. The inert atmosphere may be purified by passing it through a commercial drying tower before introduction into the casting container. It may be recirculated and re-used after passing over a bed of titanium metal maintained at approximately 1500 F. and a bed of magnesium metal maintained at approximately 1100 F. Because of the relatively high volatility of beryllium and/ or aluminum at the arc temperature, it has been found advantageous to maintain the pressure of the inert atmosphere within the casting container at substantially atmospheric pressure or slightly above-for example, up to about 15.5 pounds per square inch. In operation, the casting container is first evacuated and then filled with the inert gas, and thereafter a positive pressure of gas is maintained in the casting container at a pressure of atmospheric or slightly above. When carbon is used, the partial pressure of carbon monoxide in the melting chamber is preferably kept below about 100 microns. In some cases, this may require circulation of the purified inert gas through the chamber.

One suitable form of apparatus for use in forming, sintering and melting the powder rod is 10 disclosed in the copending application of Edgar K. Leavenworth, Serial No. 787,797, filed November 24, 1947, now Patent 2,651,952.

It has not been possible to hot-work alloys containing beryllium in excess of .25%, but such alloys have highly desirable properties when used in an unworked state. Thus, molybdenum-base alloys containing beryllium in amounts up to 7% not only may be given the above-described age hardness by heat-treatment, but exhibit high ascast hardness and a fine grain structure. More over, the alloys of higher beryllium content have a relatively low melting point and, therefore, may be produced by melting the constituents in a zirconium oxide crucible in a furnace containing an inert atmosphere. This is particularly true of molybdenum-beryllium alloys containing from 6% to 7% beryllium, which become entirely molten at temperatures in the range of 3400 F. to 3600 F.

It is known that beryllium in certain forms is highly toxic to humans. The toxic hazards, if any, involved in the production, heat-treating and forging of alloys of the present invention have not been determined but, pending further information, caution has been exercised, particularly during forging operations, to avoid inhaling fumes from the heated metal.

All of the proportions given are percentages by weight in the final alloy.

What is claimed is:

1. A process for hardening a molybdenumbase alloy containing not more than .05% oxygen and from .03% to 7% beryllium, the minimum beryllium increasing from .03% to .08% as the oxygen content increases from .001% to .05%, which comprises holding the alloy at a temperature of at least 3200 F. for at least one hour, quenching the alloy, and thereafter age hardening the alloy at a temperature between 1600 F. and 2000 F.

2. A process as defined in claim 1 for hardening a molybdenum-base alloy containing at least molybdenum, from .03% to .25% beryllium and not more than .05% oxygen, the minimum beryllium increasing from .03% to .08% as the oxygen content increases from .00l% to .05%.

3. A process as defined in claim 1 for hardening a molybdenum-base alloy containing at least 85% molybdenum, from .05% to .15% beryllium and not more than .05% oxygen, the minimum beryllium increasing from .05% to .10% as the oxygen content increases from .001% to .05%.

4. A process for hardening a molybdenum-base alloy containing not more than .05% oxygen and from .03% to 7% beryllium, the minimum beryllium increasing from .03% to .08% as the oxygen content increases from .001 to .05%, which comprises holding the alloy at a temperature of at least 3200 F. for at least one hour, quenching the alloy in a molten bath of an aluminum-silicon alloy, said bath being at a temperature between 1350 F. and 1600 F., and thereafter age hardening the alloy at a temperature between 1600 F. and 2000 F.

5. A process as defined in claim 4 for hardening a molybdenum-base alloy containing at least 85% molybdenum, from .03% to 25% beryllium and not more than .05% oxygen, the minimum beryllium increasing from .03% to .08% as the oxygen content increases from .001% to .05%.

6. A process as defined in claim 2 for hardening a molybdenum-base alloy containing at least 85% molybdenum, from .05% to .10% beryllium and not more than .05% oxygen, the minimum beryl- I FGEETGN PATENTST Number countr Date 370,566" Great Britain Apr; 14,5-1942" OTHER REFERENCES" Parkeet'aL, Melting of Molybdenum :in-the Vacuum Arc, Amer; vInst. of Mining and Metal-- lurgical Engineers, -vol. 171, 1-947,'pages 416-430;-

Kesseler ef; ah, Preprint No. 33 (1999) of paper presented at the Amen Soar for Metals Conven- 

1. A PROCESS FOR HARDENING A MOLYBDENUMBASE ALLOY CONTAINING NOT MORE THAN .05% OXYGEN AND FROM .03% TO 7% BERYLLIUM, THE MINIMUM BERYLLIUM INCREASING FROM .03% TO .08% AS THE OXYGEN CONTENT INCREASES FROM .001% TO .05%, WHICH COMPRISES HOLDING THE ALLOY AT A TEMPERATURE OF AT LEAST 3200* F. FOR AT LEAST ONE HOUR, QUENCHING THE ALLOY, AND THEREAFTER AGE HARDENING THE ALLOY AT A TEMPERATURE BETWEEN 1600* F. AND 2000* F. 